Sure, GPU is a great boost for Dyverso (and only Dyverso) in RF. You have to stay within the VRAM, but that is fine for several millions of particles, which should be fine for most small scale fluids. But I am not a hardware expert and I am simply using the recommended drivers in W10 for my Asus GTX1080Ti.

When you say "boost", does that mean that Dyverso can use the CPU and GPU at the same time? My GPU is kind of old, and was not the most powerful even when it was new so I'm almost afraid to even try it.

you can use Dyverso solvers with or without the GPU-acceleration on. Best is a graphic-card with many computation cores and a decent amount of video RAM. The Dyverso system currently uses only one GPU at the time. I see here very nice speed increases with a good GPU and Dyverso in the standalone and in the plugin version of RF.http://support.nextlimit.com/display/rf2016docs/GPU

When you say "boost", does that mean that Dyverso can use the CPU and GPU at the same time? My GPU is kind of old, and was not the most powerful even when it was new so I'm almost afraid to even try it.

If your GPU is old - how old is old? - then you might get better results with CPU, you just have to test both ways and find what is the speedier one.